1. Field of the Invention
This invention relates to an air conditioning apparatus for a vehicle, in which a passage in an air conditioning case is partitioned into a first air passage through which inside air flows and a second air passage through which outside air flows. Inside air having been heated re-circulates and is blown out from a foot air outlet, and outside air having a low-humidity is blown out from a defroster air outlet, to improve both heating capacity for a passenger compartment and defrosting performance for a windshield.
2. Description of Related Art
In a conventional air conditioning apparatus as disclosed in JP-A-5-124426, an inside air introduction port and an outside air introduction port of a blower unit is provided at one end of an air conditioning case, and a foot opening portion, a defroster opening portion and a face opening portion are respectively provided at the other end of the air conditioning case. In the air conditioning case, there is provided a partition plate for partitioning an interior of the air conditioning case into a first air passage extending from the inside air introduction port to the face opening portion and the foot opening portion and a second air passage extending from the outside air introduction port to the defroster opening portion. Further, a heating heat exchanger, a bypass passage through which air bypasses the heating heat exchanger, and an air mixing door are provided in each of the first and second air passages. Both of the air mixing doors are disposed respectively in the first and second air passages, and are connected to a single rotary shaft extending to both the first and second air passages to be integrally rotated.
When any one of a face mode, a bi-level mode and a foot mode is selected, inside air is introduced into both the first and second air passages during an entire inside air mode, or outside air is introduced into both the first and second air passages during an entire outside air mode. When a defroster mode is selected, only outside air is introduced into both the first and second air passages. Further, when a foot/defroster mode is selected, an inside/outside air double layer flow mode (hereinafter referred to as "double layer flow mode") is selected so that inside air is introduced into the first air passage and outside air is introduced into the second air passage.
Because inside air is sucked from the inside air introduction port and outside air is sucked from the outside air introduction port during the double layer flow mode, pressure loss (i.e., air-flow resistance) is reduced and a flow rate of air is increased as compared with the entire outside air mode. However, an air conditioning apparatus which can set the double layer flow mode is generally mounted in a vehicle where heat generated in an engine is too small to heat cooling water with engine sufficiently. Therefore, in this case, when the double layer flow mode is set and the flow rate of air is increased, the temperature of air blown from a heating heat exchanger which heats air using the cooling water of the engine as a heating source is decreased. Thus, heating capacity for the passenger compartment is decreased.